In recent years, as an increased density and an increased integration degree are required in manufacturing semiconductor devices, multi-layered wiring structures have been increasingly used for circuitry. Under the circumstances, embedding techniques for electrical connection between layers have become important at contact holes or trenches used as connection portions between a Si substrate serving as a lower layer and wiring layers serving as upper layers.
In order to make an ohmic connection between a Si substrate serving as a lower layer and a metal layer (plug) such as a tungsten (W) film or the like used for an embedment of contact holes, trenches or via holes, a Ti film is formed inside the contact holes or the via holes before the embedment and, if necessary, a TiSi film is formed by a reaction between Ti and underlying Si. Thereafter, a TiN film serving as a barrier film is formed.
Such Ti film has been conventionally formed by physical vapor deposition (PVD). However, chemical vapor deposition (CVD) having further increased step coverage is frequently used to satisfy recent devices having smaller sizes and higher integration degrees.
A technique for forming a Ti film by using plasma CVD has been suggested (e.g., Japanese Patent Application publication No. 2004-197219), wherein TiCl4 gas, H2 gas and Ar gas are used as a film forming gas used for CVD formation of the Ti film; the film forming gas is introduced into a chamber through a shower head; and, by supplying a high frequency power to a parallel plate electrode while heating a semiconductor wafer by a stage heater, the film forming gas is converted to a plasma thereby making the TiCl4 gas react with the H2 gas.
Although, however, recent semiconductor devices become scaled down, plasma damages such as breakdown of devices on semiconductor wafers are caused due to using the plasma in forming the Ti film by the conventional CVD. As the recent semiconductor devices become scaled down, such plasma damages cannot be ignored.